This invention relates to a method of measuring an effective heating power applied to a workpiece at a position to be heated by a high-frequency heating apparatus.
High-frequency heating apparatus employ an oscillating circuit for converting AC power into high-frequency AC power to develop an electric potential in a workpiece, causing heating because of I.sup.2 R losses. However, it is very difficult to provide direct measurement of the effective heating power applied to the workpiece at a position to be heated since there is no device capable of measuring AC power at a high frequency exceeding 20 kHz. For this reason, it is the current practice to infer the effective heating power from the DC power applied to the oscillating circuit, resulting in poor accuracy of measurement of the effective heating power.